A number of patents and publications are cited herein in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Each of these references is incorporated herein by reference in its entirety into the present disclosure, to the same extent as if each individual reference was specifically and individually indicated to be incorporated by reference.
Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise,” and variations such as “comprises” and “comprising,” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a pharmaceutical carrier” includes mixtures of two or more such carriers, and the like.
Ranges are often expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment.
This disclosure includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Cancer and RAS
RAS proteins are small-guanine nucleotide binding proteins that are downstream of growth factor, cytokine and hormone receptors. These cell surface receptors activate proteins called guanine-nucleotide exchange factors (GNEFs), which replace GDP for GTP on RAS proteins, stimulating RAS activation. Other proteins called GTPase-activating proteins (GAPs) stimulate the intrinsic GTPase activity of RAS, thereby promoting GTP hydrolysis and returning RAS to its inactive GDP-bound state. Activated RAS binds to several effector proteins, including phosphoinositide 3-kinase (PI3K), the RAF family of protein kinases, and the Rat guanine-nucleotide exchange factor. These effectors in turn regulate the activity of the signalling pathways that control cell proliferation, senescence, survival and differentiation. There are three RAS genes in mammals called HRAS, KRAS and NRAS and they serve overlapping but non-conserved functions.
RAS proteins are also important in cancer. 20-30% of human tumours harbour somatic gain-of-function mutations in one of the RAS genes. Most commonly these involve the codons for glycine 12 (G12), glycine 13 (G13) and glutamine 61 (Q61) and these mutations impair, through different mechanisms, the GAP-stimulated intrinsic GTPase activity of RAS, trapping it in the active GTP-bound state and allowing it to promote tumorigenesis. See, e.g., Downward, 2003; Young et al., 2009; and Bos, 1989.
TABLE 1Frequency of RAS Mutatations in Different Types of CancersTumour TypeFrequencyPancreas90%Thyroid (Undifferentiated papillary)60%Thyroid (Follicular)55%Colorectal45%Seminoma45%Myelodysplastic syndrome (MDS)40%Lung adenocarcinoma (non-small-cell)35%Liver30%Acute myelogenous leukemia (AML)30%Melanoma15%Bladder10%Kidney10%RAS and BRAF
Active RAS proteins activate several downstream effectors, including the proteins of the RAF family. There are three RAF proteins, ARAF, BRAF and CRAF. Activated RAF phosphorylates and activates a second protein kinase called MEK, which then phosphorylates and activates a third protein kinase called ERK. ERK phosphorylates a multitude of cytosolic and nuclear substrates, thereby regulating cell processes such as proliferation, survival, differentiation and senescence.
BRAF is important in cancer, because it is mutated in about 2% of human cancers, particularly in melanoma (43% of cases), thyroid (45%), ovarian (10%), and colorectal (13%) cancers. In contrast, ARAF and CRAF mutations are very rare in human cancer. Notably, however, in cancer cells, oncogenic RAS does not signal through BRAF, but instead signals exclusively through CRAF to activate MEK.
Over 100 different mutations have been described in BRAF in cancer, but a single mutation (a glutamic acid substitution for the valine at position 600) accounts for about 90% of the mutations that occur. This mutant activates BRAF 500-fold, and allows it to stimulate constitutive ERK and NFkB signalling, stimulating survival and proliferation. Consequently, V600EBRAF can transform cells such as fibroblasts and melanocytes. Inhibition of V600EBRAF in cancer cells inhibits cell proliferation and induces apoptosis in vitro, and in vivo it suppresses tumor cell growth, validating V600EBRAF as a therapeutic target.
In the vast majority of cancers, BRAF and RAS mutations are mutually exclusive. This provides genetic evidence to suggest that these proteins are on the same pathway and that they drive the same processes in cancer cells. However, there are clear differences between oncogenic BRAF and oncogenic RAS functions in cancer cells. First, RAS activates several pathways, whereas BRAF is only known to activate the MEK/ERK pathway. As a consequence, BRAF mutant cells are more dependent on MEK/ERK signalling and so are considerably more sensitive to BRAF or MEK inhibitors than cell in which RAS is mutated. See, e.g., Garnett et al., 2004; Wellbrock et al., 2004; Gray-Schopfer et al., 2007; Solit et al., 2006.
Related Compounds
Niculescu-Duvaz et al., 2006 (WO 2006/043090 A1), describes the following classes of compounds at pages 41 and 43 therein. The compounds are described as BRAF inhibitors useful for the treatment of cancer, especially mutant BRAF cancer.

Additionally, Niculescu-Duvaz et al., 2006 provides the following examples:

Niculescu-Duvaz et al., 2007 (WO 2007/125330 A1), describes the following classes of compounds at pages 57 and 58 therein. The compounds are described as BRAF inhibitors useful for the treatment of cancer, especially mutant BRAF cancer.

Additionally, Niculescu-Duvaz et al., 2007 provides the following examples:

The present invention provides alternative compounds, which are characterized by a particular combination of structural motifs, and which provide surprising and unexpected activity (e.g., activity against mutant RAS cancers), for example, as compared to one or more of the structurally-related known compounds.
Although structurally-related compounds are known as BRAF inhibitors, it would not have been predicted that the claimed compounds are active against mutant RAS cancers.